What should I track for accurate rotation stabilization? Or, how can I stabilize motion timelapse?
Rotational stabilisation requires 2 points/trackers that remain stationary relative to each other not the edge of frame or camera.

If that isn't available then your other solution will require a good 3d solve, from lots of trackers. But it sounds like you may not have much to track there either.

Perhaps you could use 2 planar tracks they tend to track features that cover an area instead of a point.